AI-enhanced Citizen Science Discovers Cometary Activity on Near-Earth Object (523822) 2012 DG61

We are searching for new active asteroids using data from the Subaru Hyper Suprime-Cam (HSC) Public Data Release 3 (PDR3). The active asteroids are a poorly understood class of asteroids, which have orbits similar to other asteroids but exhibit tails or comae like comets. Of the over 1.4 million catalogued minor planets, most of which are main belt asteroids, fewer than 100 of the asteroids have exhibited activity, and roughly half of those are thought to be driven by water ice. The true fraction and solar system distribution of active asteroids is poorly known as most have been discovered serendipitously by a variety of methods. In this work, we search for activity among the known asteroids using one of the deepest wide-area public datasets available, the HSC PDR3. The goal of this work is to discover new active asteroid candidates and recurring activity in known active asteroids in archival data, collect contemporary images of those asteroids using ground based telescopes, and assess the true rate of active asteroid activity in a consistent manner using a large dataset. This will lead to insights into the present day distribution of water ice in our solar system.The HSC PDR3 has been collected using one of the largest ground-based optical telescopes, the 8.2 m Subaru telescope atop Maunakea in Hawaii which regularly achieves image quality better than 0.7 arcseconds yielding single-image depths of 25 to 25.5 magnitudes in the typical exposure times used for the PDR3. In addition, HSC itself has an extremely wide field of view, about 1.8 square degrees, for such a large telescope. Over 13,000 fields were imaged in good conditions with HSC as part of the PDR3, representing over 23,000 square degrees. The PDR3 dataset was collected for scientific purposes unrelated to the asteroids but many fields contain serendipitous images of asteroids. We have cross-correlated the PDR3 fields and the Minor Planet Database using the SkyBoT project and find that over 230,000 minor planets (over 15% of all minor planets and the vast majority asteroids) were serendipitously imaged in the dataset for a total of over 1.6 million minor planet images. We have begun the process of constructing thumbnail images of these minor planets from the full HSC PDR3 data release and expect to finish this year.Initially, we are examining images by eye ourselves to determine activity candidates. However, we will launch a Citizen Science campaign akin to activeasteroids.net, which has to date only used data from the DECam public archive. This will allow us to mobilize volunteers to examine more images than we can reliably categorize ourselves. We present first results from this work including an assessment of activity levels for thousands of asteroids most likely to exhibit activity including: previously known active asteroids, distant C-type main belt asteroids, and Centaurs on unstable orbits that could have recently moved inward from the trans-Neptunian region.Figure 1: One of 4 images from the HSC PDR3 archive of known active outer main belt asteroid 331P/Gibbs, exhibiting a faint linear tail.Figure 2: One of 17 images from the HSC PDR3 archive of known Jupiter family comet 242P/Spahr, exhibiting a tail. While not a primary target of this work, many comets are present in the HSC PDR3.

All near-Earth asteroids (NEAs) that reach sufficiently small perihelion distances will undergo a so-called super-catastrophic disruption. The mechanisms causing such disruptions are currently unknown or, at least, undetermined. To help guide theoretical and experimental work to understand the disruption mechanism, we use numerical simulations of a synthetic NEA population to identify the resonant mechanisms that are responsible for driving NEAs close to the Sun, determine how these different mechanisms relate to their dynamical lifetimes at small heliocentric distances and calculate the average time they spend at different heliocentric distances. Typically, resonances between NEAs and the terrestrial and giant planets are able to dramatically reduce the perihelion distances of the former. We developed an algorithm that scans the orbital evolution of asteroids and automatically identifies occurrences of mean motion and secular resonances. We find that most near-Sun asteroids are pushed to small perihelion distances by the 3:1J and 4:1J mean-motion resonances with Jupiter, as well as the secular resonances ν6, ν5, ν3, and ν4. The time-scale of the small-perihelion evolution is fastest for the 4:1J, followed by the 3:1J, whereas ν5 is the slowest. Approximately 7 per cent of the test asteroids were not trapped in a resonance during the latest stages of their dynamical evolution, which suggests that the secular oscillation of the eccentricity due to the Kozai mechanism, a planetary close encounter, or a resonance that we have not identified pushed them below the estimated average disruption distance.

Active asteroids are a mysterious population of objects on asteroid-like orbits that display comet-like activity produced by a diverse variety of mechanisms, providing glimpses of the ongoing evolution of the asteroid belt and near-Earth objects. We report the identification of a new active asteroid 2008 BJ22, from images obtained by the Subaru Telescope in 2008. The object was not detected in earlier Canada–France–Hawaii Telescope images obtained in 2005 down to a 3σ limiting magnitude of m r ∼ 24, corresponding to a V-band absolute magnitude of H V > 18.4, more than 3 mag fainter than the absolute magnitude computed from 2008 data. Analysis of later images obtained by the Dark Energy Camera on the 4.0 m Victor M. Blanco Telescope in 2013 set the object’s current V-band absolute magnitude at H V > 19.3. These results suggest that 2008 BJ22 was discovered in an active state in 2008 January.

Background/Question/Methods Citizen science projects engage individual volunteers or groups to observe, measure, and contribute data to scientific studies. CENS is building a collection of mobile phone and web-based tools to make the citizen scientist experience more engaging and flexible. CENS is an NSF-funded Information and Technology Center that employs graduate students from Computer Science and Electrical Engineering at UCLA to create open-source software that is environmentally and socially responsible. The overarching goal of the Networked Naturalist project is to enhance participatory learning experiences through citizen science campaigns and help transform the associated learning process. We are collaborating with national field campaigns, such Project BudBurst, and also with the National Park Service to increase participation and retention in citizen scientist campaigns through two main avenues afforded by the use of new technologies: (1) to offer new methods for data collection, primarily using mobile phones, through text, picture, and smart-phone applications, and (2) to provide immediate feedback and automated, engaging analysis of data for informal learning opportunities. We are working to create a robust data collection system to enhance citizen science by ensuring data quality and improving data submission, and to transform participation into an active learning, engaging experience. Results/Conclusions Our experience with volunteers for software testing at UCLA and at the National Park Service has indicated that using mobile phones is an efficient method for collecting environmental and location data and raises public awareness of environmental issues through attracting the attention of the mass media. Individual participation in the What’s Invasive! project by volunteer citizen scientists seems to have been limited by smartphone application availability (iPhone app is currently only available for Santa Monica), although methods for making observations based on text and picture messaging are also available. We have found that running short-term "campaigns" partnered with NPS officials and groups such as schools has been the most effective in not only education-related efforts but also in efficiently identifying and locating species and objects of interest using mobile phones.

Diet of Norwegian coastal cod (Gadus morhua) studied by using citizen science

Monitoring of Asteroids in Cometary Orbits and Active Asteroids

We have studied the evolution of near-Earth asteroid (NEA) families and pairs to inform future searches. To do so, we integrated clusters of simulated NEAs with different initial conditions, namely the orbital inclination, ejection speed, and the effects of mean-motion resonances on the parent body prior to breakup while also varying the orbit, mass, and number of perturbing planetary bodies. We studied the orbital element dispersion rates of NEA family members and found a power-law increase in those families whose orbits brought them close to a planet. This allowed us to conclude that family dispersion is significantly affected by the Kozai–Lidov effect due to oscillations in the eccentricity, and that the rate of dispersion is slowest at high inclination relatively far from the nearest planet. In most cases, the ejection speed of the initial breakup does not affect the dispersion, except within weaker mean-motion resonances where more violent breakups will result in the ejection of a fraction of the asteroids, causing a large increase in dispersion. Within mean-motion resonances, where Kozai–Lidov oscillations are slowed, increases in the dispersion of a family are delayed, leading them to be identifiable for longer.

The study of active asteroids is a relatively new field of study in Solar System science, focusing on objects with asteroid-like orbits but that exhibit comet-like activity. This field, which crosses traditionally drawn lines between research focused on inactive asteroids and active comets, has motivated reevaluations of classical assumptions about small Solar System objects and presents exciting new opportunities for learning more about the origin and evolution of the Solar System. Active asteroids whose activity appears to be driven by the sublimation of volatile ices could have significant implications for determining the origin of the Earth’s water—and therefore its ability to support life—and also challenge traditional assumptions about the survivability of ice in the warm inner Solar System. Meanwhile, active asteroids whose activity appears to be caused by disruptive processes such as impacts or rotational destabilization provide exciting opportunities to gain insights into fundamental processes operating in the asteroid belt and assessing their effects on the asteroid population seen in the 21st century.

Numerical simulations of particles placed in orbital resonances in the main asteroid belt show that the typical dynamical lifetimes of objects that could become near-Earth asteroids or meteorites are only a few million years, with the majority destroyed by being transferred to Jupiter-crossing orbits or being driven into the sun. Particles that fortuitously migrate to the terrestrial planet region may be pushed to high-inclination orbits by resonances but are still dynamically eliminated on time scales of ∼10 million years. These shorter lifetimes may require a reassessment of our qualitative understanding about near-Earth asteroids and meteorite delivery.

The object P/2013 P5 PANSTARRS was discovered in August 2013, displaying a cometary tail, but its orbital elements indicated that it was a typical member of the inner asteroid main belt. We monitored the object from 2013 August 30 until 2013 October 05 using the CFHT 3.6 m telescope (Mauna Kea, HI), the NTT (ESO, La Silla), the CA 1.23 m telescope (Calar Alto), the Perkins 1.8m (Lowell) and the 0.6 m TRAPPIST telescope (La Silla). We measured its nuclear radius to be r < 0:25 0:29 km, and its colours g 0 r 0 = 0:58 0:05 and r 0 i 0 = 0:23 0:06, typical for an S-class asteroid, as expected for an object in the inner asteroid belt and in the vicinity of the Flora collisional family. We failed to detect any rotational light curve with an amplitude <0.05 mag and a double-peaked rotation period <20 h. The evolution of the tail during the observations was as expected from a dust tail. A detailed Finson-Probstein analysis of deep images acquired with the NTT in early September and with the CFHT in late September indicated that the object was active since at least late January 2013 until the time of the latest observations in 2013 September, with at least two peaks of activity around 2013 June 14 10 d and 2013 July 22 3 d. The changes of activity level and the activity peaks were extremely sharp and short, shorter than the temporal resolution of our observations ( 1 d). The dust distribution was similar during these two events, with dust grains covering at least the 1‐1000 m range. The total mass ejected in grains <1 mm was estimated to be 3:0 10 6 kg and 2:6 10 7 kg around the two activity peaks. Rotational disruption cannot be ruled out as the cause of the dust ejection. We also propose that the components of a contact binary might gently rub and produce the observed emission. Volatile sublimation might also explain what appears as cometary activity over a period of 8 months. However, while main belt comets best explained by ice sublimation are found in the outskirts of the main belt, where water ice is believed to be able to survive buried in moderately large objects for the age of the solar system deeply, the presence of volatiles in an object smaller than 300 m in radius would be very surprising in the inner asteroid belt.

An apparent discrepancy between the number of observed near-Earth objects (NEOs) with small perihelion distances (q) and the number of objects that models predict, has led to the conclusion that asteroids get destroyed at non-trivial distances from the Sun. Consequently, there must be a, possibly thermal, mechanism at play, responsible for breaking up asteroids asteroids in such orbits.We studied the dynamical evolution of ficticious NEOs whose perihelion distance reaches below the average disruption distance q_dis=0.076 au, as suggested by Granvik et al. (2016). To that end, we used the orbital integrations of objects that escaped from the main asteroid belt (Granvik et al. 2017), and entered the near-Earth region (Granvik et al. 2018). First, we investigated a variety of mechanisms that can lower the perihelion distance of an object to a small-enough value. In particular, we considered mean-motion resonances with Jupiter, secular resonances with Jupiter and Saturn (v_5 and v_6) and also the Kozai resonance.We developed a code that calculates the evolution of the critical argument of all the relevant resonances and identifies librations during the last stages of an object's orbital evolution, namely, just before q=q_dis. Any subsequent evolution of the object was disregarded, since we considered it disrupted. The accuracy of our model is ~96%.In addition, we measured the dynamical 'lifetimes' of NEOs when they orbit the innermost parts of the inner Solar System. More precisely, we calculated the total time it takes for the q of each object to go from 0.4 au to q_dis (&amp;#964;_lq). The outer limit of this range was chosen such because it is a) the approximate semimajor axis of Mercury, and b) an absence of sub-meter-sized boulders with q smaller than this distance has been proposed by Wiegert et al (2020). Combining this measure with the recorded resonances, we can get a sense of the timescale of each q-lowering mechanism.Next, for a more rigorous study of the evolution of the NEOs with q

A study of photometric observations of (3200) phaethon from Lulin Observatory

As a recently recognized class of objects exhibiting apparently cometary (sublimation-driven) activity yet orbiting completely within the main asteroid belt, main-belt comets (MBCs) have revealed the existence of present-day ice in small bodies in the inner solar system and offer an opportunity to better understand the thermal and compositional history of our solar system, and by extension, those of other planetary systems as well. Achieving these overall goals, however, will require meeting various intermediate research objectives, including discovering many more MBCs than the currently known seven objects in order to ascertain the population's true abundance and distribution, confirming that water ice sublimation is in fact the driver of activity in these objects, and improving our understanding of the physical, dynamical, and thermal evolutionary processes that have acted on this population over the age of the solar system.

Protest in Progress/Progress in Protest

We present a study of the newly discovered main-belt comet P/2008 R1 (Garradd), an object with the dynamical characteristics of an asteroid and the physical characteristics of a comet. Photometry sets a limit to the effective radius of the nucleus at re < 0.7 km (red geometric albedo 0.05 assumed). The coma shows a secular fading in our data caused by the escape of dust particles from the near-nucleus environment. The optical reflection spectrum is a nearly neutral continuum devoid of gaseous emission lines, from which we derive a limit to the cyanide (CN) radical production rate of Q CN< 1.4 × 1023 s–1 and infer a mass-loss rate <1.5 kg s–1 at the time of our observations. Unlike the first-reported main-belt comets, P/2008 R1 is not dynamically stable. The nearby 8:3 mean-motion resonance with Jupiter induces dynamical instability on timescales 20-30 Myr. Hence, we conclude that P/2008 R1 has recently arrived from a more stable source elsewhere. The high Tisserand parameter of the orbit (in fact, with TJ = 3.216 it is the highest of any comet) points to a source in the asteroid belt itself, instead of in the Kuiper belt (putative source of the Jupiter family comets). We infer that P/2008 R1 is an icy body from the outer asteroid belt in which sublimation has been triggered by rising temperatures resulting from a decreasing perihelion distance.